The present invention relates generally to the installation of a wood burning stove or "insert" into a masonry fireplace and, more particularly, to an adjustable fitting for positively connecting such an insert to a vent pipe positioned within the flue liner of a fireplace.
Wood burning fireplaces have been a common heat source for centuries and provide an inner warmth and satisfaction above and beyond any heat which is provided by the fire. Accordingly, one or more fireplaces can be found in many homes. Unfortunately, in spite of the pleasure of a wood fire, the use of a fireplace actually withdraws heated air from a modern house and hence, adds to the load placed on a central heating system resulting in higher fuel costs.
Since fuel costs have increased in the recent past and probably will continue to increase, more efficient ways of enjoying the "warmth" of a wood fire have been pursued. Heating efficiency of wood burning can be greatly increased by using a stand alone wood stove instead of a fireplace. However, such wood stoves occupy space within a home and to be safe require fireproofing of the areas surrounding the stove, for example by brickwork, or other fireproof material, such that their installation not only robs otherwise useable space from the home but also can be expensive. Accordingly, more efficient ways of operating a fireplace have been sought and resulted in the fireplace insert which is a wood stove which is fitted within or "inserted" into a fireplace opening.
Oftentimes inserts are installed by simply removing a fireplace damper and fitting the insert into the fireplace such that flue gases from the insert enter a smoke chamber of the fireplace and exit through a flue liner of the fireplace chimney. Such simple installations unfortunately reduce the effectiveness of the insert since there is no true seal between the fireplace opening and the surrounding edges of the insert and heated air from the house is still drawn up through the chimney. More importantly, a masonry fireplace has excessive internal surface area and many times the air flow capacity that is required by an insert such that the flue gases are quickly cooled allowing them to condense and deposit creosote within the fireplace and along the interior surfaces of the flue liner of the chimney. While some creosote deposits can be removed by regular cleaning performed by a competent chimney sweep, others can only be removed by heat. In any event, creosote deposits create a fire hazard within the fireplace and flue liner.
In an effort to overcome continuing heat loss and fire hazards, "positive connection" systems have been developed wherein a conduit is extended from the insert through the throat area of a removed damper of a masonry fireplace and sealed at the damper by means of insulation or otherwise. Positive connection systems route the flue gases substantially through the smoke chamber and more directly into the flue liner of the masonry fireplace chimney. Positive connection systems may in fact substantially seal the conduit or pipe coming from the insert to the bottom of the flue liner of a chimney, for example, as disclosed in U.S. Pat. No. 4,683,623. While positive connection systems substantially eliminate the loss of heated air from inside a house, the surface area and air flow capacity of the flue liner of a masonry fireplace still result in excessive production of creosote such that the fire hazard of the insert remains.
The best available solution to the dual problems of the installation of a wood burning insert into a masonry fireplace will be referred to herein as a "direct connection" system. In a direct connection system, an appropriately sized flue pipe is inserted through the flue liner of the fireplace chimney to thereby reduce its surface area and air flow capacity to that required by the insert. The flue pipe is positively sealed to the insert and also sealed at the top of the fireplace chimney by means of insulation and possibly masonry fill or otherwise such that any heated air from the inside of the house as well as heat transferred through the flue pipe tends to increase the stack temperature and thus improve the draw of the insert and reduce creosote formations within the flue pipe.
While direct connection systems provide the best and safest installation of an insert into a masonry fireplace, they are relatively expensive since preferably the flue piping is constructed of stainless steel, and, in the past, each installation had to be substantially custom fitted. Even the system disclosed in the cited patent which only provides for positive connection and not direct connection, is for all practical purposes a customized installation due to the complex nature of the interconnection devices and the installation difficulties which are apparent from a review of the patent.
In an attempt to hold down insert installation costs, one of the less than satisfactory arrangements, i.e., simply placing the insert into a fireplace or providing positive connection, have normally been utilized. Even when a direct connection system has been installed, oftentimes the interconnecting flue pipes have been made of an inferior grade of stainless steel which helps hold down costs, but results in a reduced life expectancy for the flue system of the insert. For example, 304 stainless, which is subject to acid damage, may be used for reduced cost and provide an approximate five year lifetime while 316 stainless, which is more expense and resistant to acid damage, would provide a preferred lifetime of approximately 15 to 25 years. Further, 304 stainless tends to deflect at temperatures produced during a chimney fire while 316 stainless does not.
Customizing is required in direct connection systems for interconnecting a wood stove insert to a flue pipe inserted into the flue liner of a fireplace chimney since inserts vary from maker to maker and masonry fireplaces are customized and hand built resulting in widely varying internal dimensions. This results in substantial variations in the horizontal distances between the flue outlet of a fireplace insert and the flue pipe inserted within the flue liner of a fireplace chimney.
Accordingly, there is a need for a flue fitting which can be adjustably adapted to accommodate varying horizontal distances between insert flue outlets and flue pipes to which they are to be connected to substantially reduce the amount of time and effort required in properly installing a direct connection system. Such an adjustable fitting will permit manufacture in large quantities prior to installation since the fitting can be readily adjusted on site to accommodate a large variety of inserts and fireplaces thus avoiding customized installation. By manufacturing the adjustable fittings in large quantities, not only can the cost be reduced, but also the fittings can be constructed from higher quality stainless steel, such as 316 stainless steel, which will last longer and provide more durability than many customized systems which frequently are constructed from cheaper 304 stainless steel to provide reduced cost installation.